The present invention relates to diene rubber compositions reinforced with white fillers, which can be used for the manufacture of tires or semi-finished products for tires and, in particular, tire treads.
The invention pertains to an aluminum based reinforcing white filler and to diene rubber compositions containing this filler.
In order to reduce fuel consumption and pollution emitted by motor vehicles, major attempts have been made by tire designers to obtain tires having all of the following characterisics: very low rolling resistance, improved grip both on dry ground and on wet or snow-covered ground, and very good wear resistance.
Numerous solutions have thus been proposed to lower the rolling resistance and to improve the grip of tires, but these have generally resulted in a very great decline in the wear resistance.
It is well known that the incorporation of conventional white fillers, such as silica (SiO2), alumina (Al2O3), titanium oxide (TiO2), chalk, talc, clays such as bentonite or kaolin for example, in rubber compositions used for the manufacture of tires and, in particular, of treads, results in a reduction in the rolling resistance and an improvement in grip to wet, snow-covered or icy ground. However, it also results in an unacceptable decline in the wear resistance because these conventional white fillers do not have sufficient reinforcement ability with respect to such rubber compositions. For this reason, these white fillers are generally referred to as non-reinforcing fillers, or alternatively inert fillers.
One effective solution to this problem was described in Patent Application EP-A-0 501 227, which discloses a sulphur-vulcanizable diene rubber composition obtained by thermo-mechanical working of a conjugated diene copolymer and an aromatic vinyl compound prepared by solution polymerization. This composition also comprises a special highly dispersible precipitated silica as reinforcing white filler. This composition makes it possible to manufacture a tire having substantially improved rolling resistance, without affecting the other properties, in particular those of grip, endurance and, above all, wear resistance.
Other compositions having such an excellent balance between several contradictory properties would be of great interest to tire manufacturers, who would thus have different choices available to them. Furthermore, the improvement in wear resistance thus obtained might possibly be converted into a lowering of the rolling resistance by reducing the thickness of the tread. It would thus be conceivable to construct tires having an unchanged life, but which are lighter and therefore consume less energy.
During the course of their research, the Inventors have discovered a novel reinforcing white aluminum-based filler, based on an aluminum compound, which unexpectedly makes it possible to obtain a level of reinforcement at least equal to that obtained with highly dispersible silicas.